ANTI-NUTRITIONAL CONSTITUENT OF COLOCASIA ESCULENTA ...

A.2.3.5
A.2.3.6
A.2.3.6.1
A.2.3.6.2
Mineral analysis
The standard Association of Official Analytical Chemists (AOAC, 1990) method was
used to digest the samples. The digests were diluted with HCl and the mineral
composition and concentrations of Na, Ca, K, Zn, Fe and Mg were determined, using a
PerkinElmer Atomic Absorption Spectrophotometer.
Determination ofanti-nntrients
Trypsin inhibitor
The method descn1Jed by Smith et al. (1980) was used to determine the antitrypsin
activity. Trypsin activity was measured byusing BAPNA as substrate in the presence and
absence of a sample extract. p-Nitroanilide released was measured using a
spectrophotometer at 410 mn. Trypsin inlnbitor activity (TlA) was therefore expressed as
the decrease in trypsin activity per unit weight ofsample, using the formula:
2.632·D ·At
TlA S mg pure trypsin inhibited g-l sample
D is the dilution factor, At is the change in absorbance and S is the amount of sample
weighed out.
Amylase inhibitor
a-Amylase and a-amylase inhibitory activities were estimated according to the method
utilized by Bernfeld (1955). One a-amylase unit (1ill) was defined as the amount of
enzyme that will liberate IJllllol ofmaltose from the starch under the assay conditions (10
minutes, 37" C, pH 6.9). The amylase inhibitors activity (AlA) was determined as the
percentage decrease in a-amylase activity (at the stated conditions) in the presence of
Amadumbe extracts.
38